Current practice is seawater sampling requires sample acquisition in conjunction with the use of vertically profiling electronic sensors on a probe such as the CTD (conductivity-temperature-depth) probe. Sampling bottles are therefore clustered near the probe in a sampling rosette where their closure can be triggered electro-mechanically by the operator or a computer at the surface. Normally, rosette and probe fall through the water at about 0.5 m/s, but higher fall rates are very desirable in order to minimize the use of expensive station (aircraft or ship) time. The major limitation on descent speed and attitudinal stability of the assembly is the fluid drag associated with the sampling bottles in the rosette.
In typical prior devices considerable drag is associated with the closure mechanism for the sampling bottles. Typically, the closure mechanism of prior sampling bottles comprises hinged caps that pivot outwardly from the bottle periphery presenting a larger cross-sectional area to the flow and producing flow separation and stagnant regions within and around the bottles which both result in increased drag.
Although fluid drag can be reduced by decreasing the number of bottles on the rosette, this increases the required number of casts to complete a profile and hence increases station time.
An additional problem in current practice is leakage of seawater into a sample following its acquisition. Sample contamination through leakage is critically detrimental to salinity determination. Leakage occurs in response to pressure differences between the inside of a bottle and its environment as a result of changing ambient pressure during the profiling procedure.
During water sampling in winter in frozen polar seas, ice accumulation in the bottle interior, either when the bottle is initially immersed following chilling in the atmosphere or when the bottle and the contained sample are retrieved, causes sample contamination or irreversible changes in the salinity and chemical composition of the sample.
For water sampling in Arctic seas a sampling device with a cross-section of less than about 10 inches is advantageous as holes of such size can be augered with manually operated equipment. With presently available bottles only one bottle can be used per cast through such auger holes.